WO2022193367A1

WO2022193367A1 - Display panel and manufacturing method therefor

Info

Publication number: WO2022193367A1
Application number: PCT/CN2021/084274
Authority: WO
Inventors: 邹伟
Original assignee: 武汉华星光电半导体显示技术有限公司
Priority date: 2021-03-19
Filing date: 2021-03-31
Publication date: 2022-09-22
Also published as: US20230157142A1; CN113113426A

Abstract

A display panel and a manufacturing method therefor. The display panel comprises a thin-film transistor array layer (20), a light-emitting device layer (70), and a thermosensitive thin film layer (50). At least one thermistor (R) is connected in series in a light-emitting circuit consisting of a driving transistor (DTFT) and a light-emitting device (OLED), so as to reduce or eliminate attenuation of the temperature on light-emitting brightness, so that the accepted life evaluation standard in the industry can be met.

Description

Display panel and method of making the same

technical field

The present application relates to the field of display technology, and in particular, to a display panel and a manufacturing method thereof.

Background technique

In organic light-emitting diodes (OLED, Organic Light-Emitting Diode), the service life is one of the important parameters for evaluating the level of the device. In the existing small and medium-sized mass production display products, the length of the device life is directly related to the service life of the product. The decay curve of organic light emitting (OEL, Organic Electro-Luminescence) devices usually consists of short-term fast decay and long-term slow decay, which is an irreversible process. The former can be eliminated by the aging process before leaving the factory, so that only slow life decay of the EL device is involved in actual use.

However, the lifespan decay in actual products is not only related to the aging process of EL, the current mainstream Active-matrix Organic Light-Emitting Diode (AMOLED, Active-matrix Organic Light-Emitting Diode) also needs to consider the thin film transistor (TFT) at the bottom. Impact. As the mobile phone is used in different environments, such as temperature changes, it will lead to multiple factors. In the initial stage of OLED lighting, due to the influence of temperature on the mobility of TFT and EL devices, the brightness of the screen rapidly decreases by 1% to 5%. This phenomenon is called Initial. drop (initial decay). Therefore, if the industry-recognized lifespan evaluation standard is used, that is, the time it takes for the brightness to decay to 95% of the initial value (T95), the initial drop will greatly deviate from the actual lifespan of the EL, which is not conducive to device development and meeting customer needs.

It should be noted that the above description of the background technology is only for facilitating a clear and complete understanding of the technical solutions of the present application. Therefore, it should not be considered that the above-mentioned technical solutions are known to those skilled in the art just because they appear in the background art of the present application.

technical problem

The present application provides a display panel and a manufacturing method thereof, which alleviates the problem of brightness attenuation due to the influence of temperature during the initial stage of display.

technical solutions

In a first aspect, the present application provides a display panel, which includes a thin film transistor array layer, a light emitting device layer, a thermal thin film layer and a pixel driving circuit; the thin film transistor array layer includes at least one driving transistor; the light emitting device layer is formed with at least one light emitting device layer. device; a thermal film layer, the thermal thin film layer is formed with at least one thermistor; the pixel driving circuit includes a driving transistor, a thermistor and a light-emitting device; wherein, at least one thermistor is connected in series with the driving transistor and the light-emitting device. in the light circuit.

In a second aspect, the present application provides a display panel, which includes a thin film transistor array layer, a light emitting device layer, and a thermal thin film layer; the thin film transistor array layer includes at least one driving transistor; the light emitting device layer is formed with at least one light emitting device; The thin film layer is formed with at least one thermistor; wherein, the at least one thermistor is connected in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.

Based on the first aspect, in a first embodiment of the first aspect, the heat-sensitive thin film layer is adjacent to the thin film transistor array layer or the light emitting device layer.

Based on the first embodiment of the first aspect, in the second embodiment of the first aspect, the thermosensitive thin film layer is located between the thin film transistor array layer and the light emitting device layer.

Based on the first aspect, in a third implementation manner of the first aspect, the display panel further includes at least one via hole; the first end of the via hole is connected to the first end of the thermistor; the second end of the via hole is connected to the drive One of the transistor and the light-emitting device is connected; the other one of the driving transistor and the light-emitting device is connected to the second end of the thermistor.

Based on the third embodiment of the first aspect, in a fourth embodiment of the first aspect, the light emitting device layer includes an anode layer; the anode layer includes an anode; and the width of the anode is greater than or equal to that of the thermistor.

Based on the fourth implementation manner of the first aspect, in a fifth implementation manner of the first aspect, the display panel further includes a flat layer; the flat layer is located between the thin film transistor array layer and the light emitting device layer.

Based on the fifth implementation manner of the first aspect, in a sixth implementation manner of the first aspect, the heat sensitive thin film layer is located between the flat layer and the thin film transistor array layer.

Based on the fifth embodiment of the first aspect, in the seventh embodiment of the first aspect, the thermosensitive thin film layer is located between the flat layer and the light emitting device layer; the via hole is located at least in the flat layer.

Based on the third implementation manner of the first aspect, in an eighth implementation manner of the first aspect, the thermistor at least partially covers the first end of the via hole or the second end of the via hole.

In a third aspect, the present application provides a method for preparing a display panel, which includes: preparing a thin film transistor array layer, where the thin film transistor array layer includes at least one driving transistor; preparing at least one thermal thin film layer, the thermal thin film layer includes at least one thermal a thermistor; preparing a light-emitting device layer, the light-emitting device layer includes at least one light-emitting device; and connecting at least one thermistor in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.

beneficial effect

The display panel and the manufacturing method thereof provided by the present application can reduce or eliminate the attenuation of the luminous brightness caused by the temperature by connecting at least one thermistor in series in the luminous circuit formed by the driving transistor and the light emitting device, and can meet the life evaluation standard recognized in the industry , which is conducive to meeting the needs of customers.

Description of drawings

FIG. 1 is a schematic structural diagram of a display panel provided by an embodiment of the present application.

FIG. 2 is another schematic structural diagram of a display panel according to an embodiment of the present application.

FIG. 3 is a schematic structural diagram of a pixel circuit in a conventional technical solution.

FIG. 4 is a schematic structural diagram of a pixel circuit provided by an embodiment of the present application.

FIG. 5 is a schematic diagram showing the comparison of luminous lifetimes when different pixel circuits are used.

FIG. 6 is a schematic flowchart of a method for fabricating a display panel according to an embodiment of the present application.

Embodiments of the present invention

In order to make the objectives, technical solutions and effects of the present application clearer and clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

Referring to FIGS. 1 to 2 , as shown in FIG. 1 , the present embodiment provides a display panel, which includes a thin film transistor array layer 20 , a light emitting device layer 70 and a thermal thin film layer 50 ; the thin film transistor array layer 20 includes at least A driving transistor; the light-emitting device layer 70 is formed with at least one light-emitting device; the thermal film layer 50 is formed with at least one thermistor; wherein, at least one thermistor is connected in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.

It should be noted that the study found that the initial drop has a great relationship with the temperature of the screen. Therefore, the brightness of the light-emitting screen will decay rapidly in the early stage of lighting, which will lead to the failure of the life specification of the display product. To solve this problem, this embodiment proposes an Initial In the drop design method, a thermistor is connected in series in the circuit where the EL device is located, and the temperature sensitivity of the thermistor is used to compensate the current, thereby realizing the corresponding brightness compensation and solving the process limitation caused by the life problem. limit and yield loss.

For example, when the temperature rises in the early stage of operation of the light-emitting device, the current flowing through the light-emitting device decreases rapidly. At this time, the resistance of the thermistor decreases with the increase of temperature, which indirectly increases the resistance between the source and the drain of the driving transistor. The cross voltage, the Vds of the drive transistor, in turn increases the current flowing through the light-emitting device, compensating for the temperature-induced brightness drop. Conversely, when the temperature drops, the corresponding brightness compensation can also be performed.

Based on the above analysis, this embodiment does not change the process conditions of the light emitting device layer 70 and the thin film transistor array layer 20 by adding external structures, and can be applied to various light emitting material systems and OLED device structures.

It can be understood that the display panel provided by the present application can reduce or eliminate the attenuation of the luminous brightness caused by the temperature by connecting at least one thermistor in series in the luminous circuit formed by the driving transistor and the light emitting device, and can meet the life-span assessment generally recognized in the industry. standard, which is conducive to meeting the needs of customers.

In one embodiment, the thermosensitive thin film layer 50 is located between the thin film transistor array layer 20 and the light emitting device layer 70 .

In one embodiment, the display panel further includes at least one via hole 31; the first end of the via hole 31 is connected to the first end of the thermistor; the second end of the via hole 31 is connected to one of the driving transistor and the light emitting device connected; the other of the driving transistor and the light emitting device is connected to the second end of the thermistor.

Wherein, the via hole 31 may be located at least in the flat layer 30, and the via hole 31 is used to realize the electrical connection between the thermistor and the driving transistor DTFT and/or the light emitting device OLED. Therefore, based on the function of the via hole 31 , the via hole 31 may also pass through other film layers in the display panel.

In one embodiment, the light emitting device layer 70 includes an anode layer 60; the anode layer 60 includes an anode; and the width of the anode is greater than or equal to the width of the thermistor.

In one embodiment, the heat sensitive thin film layer 50 is located between the thin film transistor array layer 20 and the anode layer 60 .

Wherein, the thin film transistor array layer 20 may include a source-drain layer, and the source-drain layer includes a source electrode and a drain electrode of the driving transistor DTFT. The thermistor R may be electrically connected to one of the source and the drain of the driving transistor DTFT. Alternatively, the thermistor R may also be electrically connected to the anode of the light emitting device.

In one of the embodiments, the display panel includes a planarization layer 30 ; the planarization layer 30 is located between the thin film transistor array layer 20 and the light emitting device layer 70 .

It can be understood that the source and drain layers may be adjacent to the flat layer 30 . The depth of the via hole 31 can be reduced.

In one embodiment, the thermosensitive thin film layer 50 is located between the flat layer 30 and the light emitting device layer 70 . The thermosensitive thin film layer 50 is adjacent to the light emitting device layer 70 .

In one of the embodiments, the display panel further includes at least one of the substrate 10 and an encapsulation layer. Wherein, the substrate 10 is located on one side of the thin film transistor array layer 20 and away from the flat layer 30 . The encapsulation layer is located on one side of the light emitting device layer 70 and away from the substrate 10 .

Wherein, the substrate 10 may be, but not limited to, a glass substrate, and may also be a flexible PI substrate.

In one embodiment, on the display panel, a pixel definition layer 40 , an anode layer 60 and a light emitting device layer 70 on one side of the flat layer 30 may be disposed in sequence. A plurality of light-emitting devices may be formed in the light-emitting device layer 70, and at least one light-emitting device may include a hole injection layer (HITL), a hole transport layer (HTL), an electron blocking layer (EBL), a blue light Light Emitting Layer (EML), Hole Blocking Layer (HBL), Electron Transport Layer (ETL), Electron Injection Layer (EIL), Cathode and Light Extraction Layer (CPL).

In one embodiment, the encapsulation layer may include a first inorganic layer 80 , an organic layer 90 and a second inorganic layer 100 that are stacked in sequence. Wherein, the materials of the first inorganic layer 80 and the second inorganic layer 100 may be any one of silicon nitride, silicon oxide or silicon oxynitride.

In one embodiment, the heat-sensitive thin film layer 50 can be completed by at least one method of evaporation, magnetron sputtering, laser deposition, and etching. The material of the heat-sensitive thin film layer 50 may include, but is not limited to, inorganic materials such as MnCoNiO-based, MnCoCuO-based and the like. It can also choose a positive temperature coefficient (PTC) material according to the current rise caused by the temperature rise when the light-emitting device is working; conversely, a negative temperature coefficient (NTC) material can also be used.

Specifically, taking the NTC material as an example, when the device is in the initial stage of operation, the temperature rises and the current drops rapidly, and the thermistor will decrease the impedance with the temperature rise, thereby indirectly increasing the Vds cross-voltage of the driving transistor, thereby increasing the current and compensating for the Decreases in brightness due to temperature.

Wherein, the heat-sensitive film layer 50 may be translucent, but not limited to. The choice of transparency can be achieved by adjusting the thickness of the heat-sensitive thin film layer 50 . It can be understood that the resistance value of the thermistor can also be selected according to at least one of parameters such as the thickness of the thermal thin film layer 50, the shape and size of the thermistor.

In one embodiment, the heat-sensitive film layer 50 includes a first heat-sensitive film layer and a second heat-sensitive film layer. The first heat sensitive thin film layer may be located between the flat layer and the anode layer. The second heat-sensitive thin film layer may be located between the planarization layer and the thin film transistor array layer. Wherein, the first thermal film layer is formed with a plurality of first thermistors; the second thermal film layer is formed with a plurality of second thermistors. The first thermistor may at least partially cover one of the first end of the via hole and the second end of the via hole. The second thermistor may at least partially cover the other of the first end of the via and the second end of the via.

As shown in FIG. 2 , in one embodiment, the thermosensitive thin film layer 50 is located between the planarization layer 30 and the thin film transistor array layer 20 . The heat sensitive thin film layer 50 is adjacent to the thin film transistor array layer 20 .

As shown in FIGS. 1 and 2 , in one embodiment, the thermistor at least partially covers the first end of the via hole 31 or the second end of the via hole 31 .

Wherein, it can be understood that the display panel further includes a pixel circuit, and the pixel circuit includes a corresponding driving transistor, and the driving transistor is located in the thin film transistor array layer 20 .

Based on the above technology, in one embodiment, as shown in FIG. 3 , the pixel circuit may include a driving transistor DTFT and a light emitting device OLED. One of the source/drain of the driving transistor DTFT is used to access the first power supply signal VDD; the other of the source/drain of the driving transistor DTFT is connected to the anode of the light emitting device OLED; the cathode of the light emitting device OLED is used for The second power supply signal VSS is connected; the gate of the driving transistor DTFT is used for accessing the scan signal. Wherein, the potential of the first power supply signal VDD is higher than the potential of the second power supply signal VSS.

In one embodiment, as shown in FIG. 4 , the pixel circuit may include a driving transistor DTFT, a light emitting device OLED, and a thermistor R. One of the source/drain of the driving transistor DTFT is used to access the first power supply signal VDD; the other of the source/drain of the driving transistor DTFT is connected to the first end of the thermistor R; the thermistor R The second end of the OLED is connected to the anode of the light-emitting device OLED; the cathode of the light-emitting device OLED is used to connect the second power supply signal VSS; the gate of the driving transistor DTFT is used to connect to the scanning signal. Wherein, the potential of the first power supply signal VDD is higher than the potential of the second power supply signal VSS.

It can be understood that, compared with the pixel circuit shown in FIG. 3, the pixel circuit shown in FIG. 4 is connected in series with a thermistor R in the light-emitting circuit formed by the driving transistor DTFT and the light-emitting device OLED, and the thermistor R can be For sensing the temperature of the driving transistor DTFT and/or the light emitting device OLED.

Based on the pixel circuits shown in FIG. 3 and FIG. 4 , the light-emitting lifespans between the two are quite different. In the following, the light-emitting lifespan of the pixel circuit shown in FIG. The light emission lifetime driven by the pixel circuit becomes the improved light emission lifetime. Specifically, as shown in FIG. 5 , for sub-pixels of different colors, there are also differences in their luminous lifetimes.

For example, the upper left panel in FIG. 5 is a schematic diagram showing the comparison of white light lifetime of white sub-pixels, wherein the lower curve is the white light lifetime curve before improvement, and the upper side curve is the improved white light lifetime curve. At the starting point, that is, at 0 hours (hr) on the horizontal axis of time, the initial brightness of the white light life curve before improvement dropped sharply at the beginning, and the initial brightness of the improved white light life curve actually increased further at the beginning, and exceeded 100% brightness. At the same time, it can be seen from the comparison that after 300 hours of testing, the brightness of the white light life curve before improvement has attenuated to between 92% and 94% of the initial brightness, while the brightness of the improved white light life curve has only attenuated to 96% of the initial brightness. % to 98%.

The upper right panel in Figure 5 is a schematic diagram showing the comparison of the red light lifetime of the red sub-pixels, wherein the lower curve is the red light lifetime curve before improvement, and the upper side curve is the improved red light lifetime curve. At the starting point, that is, when the horizontal axis of time is 0 hours (hr), the initial brightness of the red light lifetime curve before improvement drops sharply at the beginning, and the initial brightness of the improved red light lifetime curve decreases relatively slowly. It can be seen from the comparison that after 300 hours of testing, the brightness of the red light life curve before improvement has attenuated to between 92% and 94% of the initial brightness, while the brightness of the improved red light life curve has only attenuated to 96% of the initial brightness. % to 98%.

The lower left panel in FIG. 5 is a schematic diagram showing the comparison of green light lifetime of green sub-pixels, wherein the lower curve is the green light lifetime curve before improvement, and the upper side curve is the green light lifetime curve after improvement. At the starting point, where the horizontal axis of time is 0 hours (hr), the initial brightness of the green light life curve before the improvement drops sharply at the beginning, and the initial brightness of the improved green light life curve first rises, and then slowly decreases. slip. The comparison shows that after 300 hours of testing, the brightness of the green light life curve before improvement has decayed to about 92% of the initial brightness, while the brightness of the improved green light life curve has only attenuated to about 97% of the initial brightness.

The lower right panel in FIG. 5 is a schematic diagram of blue light lifetime comparison of blue sub-pixels, wherein the lower curve is the blue light lifetime curve before improvement, and the upper side curve is the improved blue light lifetime curve. At the starting point, where the horizontal axis of time is 0 hours (hr), the initial brightness of the blue light lifetime curve before the improvement drops sharply at the beginning, and the initial brightness of the improved blue light lifetime curve first rises and then falls relatively slowly. It can be seen from the comparison that after 300 hours of testing, the brightness of the blue light life curve before improvement has attenuated to about 95% of the initial brightness, while the brightness of the improved blue light life curve has only attenuated to about 96.5% of the initial brightness.

Based on the above analysis, it can be seen that the use of the pixel circuit provided in the present application can significantly improve the problem of brightness attenuation in the initial stage of light emission, and can meet the life evaluation standard recognized in the industry.

As shown in FIG. 6 , in one embodiment, this embodiment provides a method for manufacturing a display panel, which includes the following steps:

Step S10 : preparing a thin film transistor array layer, where the thin film transistor array layer includes at least one driving transistor.

Step S20 : preparing at least one thermosensitive thin film layer, and the thermosensitive thin film layer includes at least one thermistor.

Step S30 : preparing a light-emitting device layer, the light-emitting device layer includes at least one light-emitting device.

And step S40 : connecting at least one thermistor in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.

It can be understood that, in the preparation method of this embodiment, the above steps do not have a strict execution order, and the preparation method that can realize the inventive concept of this embodiment can be applied to the preparation process of the display panel in this embodiment.

It can be understood that, in the preparation method of the display panel provided in this embodiment, by connecting at least one thermistor in series in the light-emitting circuit formed by the driving transistor and the light-emitting device, it can also reduce or eliminate the attenuation of the light-emitting brightness caused by the temperature. Meeting industry-recognized life-span assessment criteria helps meet customer needs.

In one of the embodiments, this embodiment provides a display device, which includes the display panel in any of the above-mentioned embodiments.

It can be understood that the display device provided by the present application reduces or eliminates the attenuation of the luminous brightness caused by the temperature by connecting at least one thermistor in series in the light-emitting circuit formed by the driving transistor and the light-emitting device, and can meet the life-span evaluation standard recognized in the industry. , which is conducive to meeting the needs of customers.

It can be understood that for those of ordinary skill in the art, equivalent replacements or changes can be made according to the technical solutions and inventive concepts of the present application, and all these changes or replacements should belong to the protection scope of the appended claims of the present application.

Claims

A display panel, comprising:

a thin film transistor array layer, the thin film transistor array layer includes at least one driving transistor;

a light emitting device layer formed with at least one light emitting device;

a thermally sensitive film layer formed with at least one thermistor; and

a pixel drive circuit, the pixel drive circuit includes the drive transistor, the thermistor, and the light-emitting device;

Wherein, at least one of the thermistors is connected in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.
The display panel of claim 1, wherein the heat-sensitive thin film layer is adjacent to the thin film transistor array layer or the light emitting device layer.
The display panel of claim 2, wherein the heat sensitive thin film layer is located between the thin film transistor array layer and the light emitting device layer.
The display panel of claim 1, wherein the display panel further comprises at least one via hole; a first end of the via hole is connected to a first end of the thermistor; a second end of the via hole The terminal is connected to one of the driving transistor and the light-emitting device; the other one of the driving transistor and the light-emitting device is connected to the second terminal of the thermistor.
The display panel of claim 4, wherein the light emitting device layer includes an anode layer; the anode layer includes an anode; and a width of the anode is greater than or equal to a width of the thermistor.
The display panel according to claim 5, wherein the display panel further comprises a flat layer; the flat layer is located between the thin film transistor array layer and the light emitting device layer; the via hole is located at least in the flat layer in the layer.
The display panel of claim 6, wherein the heat sensitive thin film layer is located between the flat layer and the thin film transistor array layer.
The display panel of claim 6, wherein the heat-sensitive thin film layer is located between the flat layer and the light emitting device layer.
The display panel of claim 4, wherein the thermistor at least partially covers the first end of the via hole or the second end of the via hole.
A display panel, comprising:

a thin film transistor array layer, the thin film transistor array layer includes at least one driving transistor;

a light emitting device layer formed with at least one light emitting device; and

a heat-sensitive film layer, the heat-sensitive film layer is formed with at least one thermistor;

Wherein, at least one of the thermistors is connected in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.
The display panel of claim 10, wherein the heat sensitive thin film layer is adjacent to the thin film transistor array layer or the light emitting device layer.
The display panel of claim 11, wherein the heat sensitive thin film layer is located between the thin film transistor array layer and the light emitting device layer.
The display panel of claim 10, wherein the display panel further comprises at least one via hole; a first end of the via hole is connected to a first end of the thermistor; a second end of the via hole is connected to the first end of the thermistor; The terminal is connected to one of the driving transistor and the light-emitting device; the other one of the driving transistor and the light-emitting device is connected to the second terminal of the thermistor.
The display panel of claim 13, wherein the light emitting device layer includes an anode layer; the anode layer includes an anode; and a width of the anode is greater than or equal to a width of the thermistor.
The display panel according to claim 14, wherein the display panel further comprises a flat layer; the flat layer is located between the thin film transistor array layer and the light emitting device layer; the via hole is located at least in the flat layer in the layer.
16. The display panel of claim 15, wherein the heat-sensitive thin film layer is located between the flat layer and the thin film transistor array layer.
The display panel of claim 15, wherein the heat sensitive thin film layer is located between the flat layer and the light emitting device layer.
The display panel of claim 13, wherein the thermistor at least partially covers the first end of the via hole or the second end of the via hole.
The display panel of claim 10, wherein the thermistor is connected in series between one of the source/drain of the driving transistor and the anode of the light emitting device.
A preparation method of a display panel, comprising:

preparing a thin film transistor array layer, the thin film transistor array layer comprising at least one driving transistor;

preparing at least one thermosensitive film layer, the thermosensitive film layer comprising at least one thermistor;

preparing a light emitting device layer, the light emitting device layer including at least one light emitting device; and

At least one thermistor is connected in series in the light-emitting circuit formed by the driving transistor and the light-emitting device.